Field of Invention
The present invention relates to technical field of hydraulic transmission control, and more particularly to a double-loop control system with a single hydraulic motor.
Description of Related Arts
As a rotating actuator, a hydraulic motor mainly drives machines for rotating, lifting and traveling. In real application, due to a relatively large inertia of a driven load, a large output torque is often required during starting and accelerating; during stably operating, much less torque is required; and during braking, a large barking torque is needed. Therefore, system pressure and displacement must be determined to select a hydraulic motor according to a maximum torque during working, which often increases a volume of the hydraulic motor and a volume of a corresponding hydraulic control system, which results in lower working efficiency of an entire system.
During rotating, lifting and traveling processes of the conventional hydraulic valve control mechanism, kinetic energy generated by rotating-braking or decelerating braking, potential energy generated during falling or traveling downhill are wasted by being transformed into heat of oil through a throttling effect of valves, and the heat is also a main reason causing hydraulic systems failure. In order to reduce the heating, an additional cooling system is needed to cool the oil, which further increases the systems energy consumption. If the wasted energy can be recycled, that not only can save energy and reduce the system installed power, but also can reduce the system failure probability and improve the production efficiency. Chinese patent application, CN 201180033048.7, discloses a hybrid power excavator which stores and utilizes the kinetic energy of rotating-braking, based on a conventional rotating control loop, a motor/generator driven together with a rotating mechanism is added. When an excavator upper portion is in rotating-braking, the motor/generator is under generator state to store the kinetic energy during the rotating-braking in super-capacitors; when an excavator upper portion is in accelerating-rotating again, the motor/generator is under motor state to drive the upper portion rotating together with an original hydraulic system, the motor/generator will stop after accelerating. The hybrid power excavator not only improves the energy efficiency of the system, but also reduces the size and power of the hydraulic system. However, the shortcomings of it are that this method is only applicable to hybrid power machines, and cost is high.
Chinese patent application, CN201010106824.9, discloses a rotating-decelerating energy recovery system for a hydraulic excavator, based on a conventional hydraulic motor system controlled by multi-way valve, two hydraulic control commutate valves are respectively set up on both sides of a hydraulic motor, and an accumulator and two pressure sensors are added. When the pressure sensors detect that the hydraulic motor is braking, the system automatically controls the hydraulic control commutate valves to change a direction, wherein an oil chamber with high pressure connects with the accumulator; when the system is in accelerating-rotating again, high-pressure oil stored in the accumulator enters a multi-way valve inlet through a solenoid valve and a check valve to realize recycling. However, the accumulator state will affect the operating speed characteristics during rotating, and the stored energy cannot be fully used.
International patent application, WO2013/003049A2, published on Jan. 3, 2013, discloses a rotating-braking energy recovery system for a hydraulic excavator, in this system a selector valve, an accumulator filling valve, an accumulator draining valve and an accumulator are set up in an separate meter-in and separate meter-out hydraulic motor control loop. The selector valve is a hydraulic control two-position three-way valve, two control chambers respectively connect with two chambers of a hydraulic motor, so that an oil port of the valve is always connected to the chamber of the hydraulic motor with a higher pressure. When the hydraulic motor is braking, high-pressure oil will charge into the accumulator through the selector valve and the accumulator filling valve to recycle braking energy; when the motor is accelerating, the accumulator provides oil into inlet chamber of the hydraulic motor through the accumulator draining valve and the selector valve to regenerate and utilize the stored braking energy. However, a storage loop and a control loop of the system can't drive the hydraulic motor at the same time, and when the storage loop individually drives the hydraulic motor, the power is insufficient, which will affect the recycling effect.
Although the above technologies are able to effectively recover energy during rotating, lifting and travelling; and the energy is used as driving force. But all of the above technologies are not able to use only one hydraulic motor to satisfy different work conditions and different load driving requirements with advantages such as simple structure, high system reliability, and high energy efficiency at the same time.